Cured cement, mortar or concrete structure embedded with metallic armatures such as iron or steel wires, rods and frames or metallic structure covered with cement, mortar or concrete to be cured has widely been used in the civil engineering and construction fields. Such cement, mortar and concrete material shall be called hereafter "cementitious material". And such structure shall be called hereafter "cementitious structure".
As well known, such cementitious material is deteriorated from the outer surface to the inner portion gradually with the lapse of years. Due to water and oxygen in air penetrated through pores and cracks of the cementitious material, the metallic armatures are to be rusted by and by which in turn accelerates deterioration of cementitious material. This vicious cycle rapidly weakens the cementitious structure as a whole to be in dangerous state.
Japanese Unexamined Patent Application Gazette No. 78764/1980 discloses a method for repairing such deteriorated of cementitious material by applying an aqueous solution of an alkali metal silicate on the surface thereof and further coating with cement paste so as to prevent exudation thereof. This method intends to prevent neutralization or deterioration of the repaired cementitious material owing to strong alkalinity of such silicate, but since such paste coating is to be cracked before long, since porous and cracked surface portion of the cementitious material itself is not improved thereby and since such alkaline silicate is to be exuded in due course of time, this method can not attain the purpose for a long term prevention of the cementitious material from deterioration.
Japanese Unexamined Patent Application Gazette No. 2639/1976 discloses a method for preventing metal armatures embedded in cementitious material from rusting by applying a liquid agent comprising a nitrite and silica sol at the surface of said cementitious structure to be penetrated therein. This is however, unsatisfactory in that such liquid agent is not of good storage stability and cannot sufficiently penetrated in cementitious material due to colloidal particle size of silica.
Japanese Unexamined Patent Application Gazette No. 20768/1983 discloses a method for improving surface layer of cementitious material by applying an aqueous solution of an alkali metal silicate as well as a condensate of sodium naphtalenesulfonate and formaldehyde. This method is fairly effective for preventing deterioration of cementitious material owing to that such liquid agent can penetrate in such material deeper than any agent of the prior arts to be made compact. Said method is, however, still unsatisfactory in that water and oxygen in air penetrated in said material, which can not be completely prevented, cause rust of metallic armatures embedded therein, which in turn causes deterioration of cementitious material.